1. Field of the Invention
The present invention relates to controlled access and more particularly to systems which are operable without a key and are especially adaptable for application in vehicles such as automobiles.
2. Description of the Prior Art
After automobiles gained general acceptance by the consuming public, mechanisms were devised for the purpose of limiting their closure and operation. The conventional key operated tumbler lock was readily available for such applications as doors, glove boxes, trunks and ignitions on automobiles, although security devices operable without a key were soon being sought.
One such system is described in U.S. Pat. No. 1,251,365 entitled Permutation Lock which involves relatively complicated interlock mechanisms using electromagnets to position tumblers in a bolt which controls the movement of a mechanical component intended to be locked. The system is button operated and the buttons must be pushed in a preselected sequential order for operation. The system is considered mechanically complex, heavy and bulky and is generally unsuited for many current day automobile applications.
In U.S. Pat. No. 1,298,177 entitled Combination Lock for Automobiles, the inventors describe a somewhat analogous system using a plurality of interchangeable keys having selected areas of conducting and nonconducting surfaces thereon such that when the keys are mechanically adjusted by the operator to a prearranged disposition, various electrical circuits are completed and the interlock is bypassed. Another very old system is described in U.S. Pat. No. 1,587,757 entitled Automobile Lock which is electromechanical in nature and is operable by properly inserting a plug into one of a plurality of receptacles and manipulating the position of the plug. The concepts in each of these two patents are feasible but impractical by current day standards because of their size, complexity and relatively inflexible codeability.
More recent variations of the relatively cumbersome locking systems described above are disclosed in U.S. Pat. No. 2,819,770 entitled Means for Securing a Motor Vehicle Against Theft and U.S. Pat. No. 2,964,733 entitled Automobiles or Like Vehicles Fitted with Theft Prevention Devices.
The inventors of Door Locking Means disclose in U.S. Pat. No. 3,353,383 a combination lock mechanism that must be properly decoded before a latch member can be actuated to allow a door to be opened. The system is operated by push buttons and is essentially mechanical in nature, being organized such that if the push buttons are not operated in the suitable sequence, not only is the latch mechanism not free to move but an alarm is thereby triggered. As is the case with much of the preceding art, the workable system is relatively complex, heavy and inflexible. Further, such mechanical systems tend to be relatively large, expensive, and limited in their applicability due to such factors as size, reliability and environmental sensitivity.
In U.S. Pat. No. 3,024,452 entitled Multi-Digit Electrical Door Lock, the inventors disclose a system which is more electrical in nature. A group of push buttons is combined with suitable circuits which respond to a preselected input. In the event the buttons are operated in a wrong sequence, the electrical circuitry causes the system to become immobilized and an alarm is initiated. The system is further characterized in that the code to which the system will respond can be changed by mechanical manipulation of provided selectors. Another concept is disclosed in U.S. Pat. No. 3,192,448 entitled Keyless Electric Lock wherein a lock bolt is actuated when the available switches are activated in a preselected sequence in order to activate a solenoid in the system.
While some of the more recent inventions are clear improvements over the preexisting art, the various security systems available can be characterized as mechanically oriented although some do involve electromechanical or electrical activation mechanisms. Nevertheless, such systems are relatively massive, complex and rigid and although their codes may be changed, such changes ordinarily require mechanical manipulation of certain variable components. The automobile industry in particular currently looks forward to a consumer oriented security system having good market acceptance. Such systems should be easily operable, include a capacity to change the access mode quickly and easily, and retain the secureness and reliability of the overall locking system in an inexpensive and rugged embodiment of reasonable size and weight.